Doctor blade for calender roll



June 1967 H. E. KUEHN 3,327,341

DOCTOR BLADE FOR CALENDER ROLL Filed Jan. 8, 1965 SheeW-Sheet 1 f I I3{I I G I 4 INVENTOR Houuoxd E. Kuehn Daw wdmwdi;

ATTORNEXS i L15 v 2 June 27, 1967 H. E. KUEHN DOCTOR BLADE FOR GALENDERROLL 3 Sheets-Sheet 2 Filed Jan. 8, 1965 OUJQXC! Kuehn Dim? W9 m MZEORNEYS June 27, 1967 H. E. KUEHN 3,327,341

DOCTOR BLADE FOR CALENDER ROLL Filed Jan. 8, 1965 5 shegtsfihget 5 B C5' w 9/566. 30 3 8 ,2 B o V 7; x

INVENTOR Howard E. Kuehn Dflw M9 Mwifi A'ITORNEY5 United States Patent"ice 3,327,341 DOCTDR BLADE FOR CALENDER ROLL Howard E. Kuehn, Orange,Conrn, assiguor to Farrel Corporation, Ansonia, Conn. Filed Jan. 8,1965, Ser. No. 424,422 Claims. (Cl. -25651) This invention relates tocalendering apparatus, and more particularly relates to doctor bladesused in conjunction therewith.

In apparatus for calendering materials, such as paper, bits of thematerial being calendered cling to the rolls. For high qualitycalendering the surfaces of the roll should be kept clean and free offoreign material in order that the material may be calendered to uniformdimensions and characteristics throughout its length and width. This isaccomplished by the provision of a doctor blade for each roll whichcontacts the roll surface along essentially its entire length and stripscontaminants from the surface of the roll as the roll moves past thedoctor blade.

The doctor blade and the support therefor extend across essentially theentire face of the roll, and means are provided at either end of thedoctor blade support for urging the doctor blade into contact with theroll at a predetermined pressure. Therefore, the contact pressureproducing means essentially acts only at the ends of the doctor blade.The length of the doctor blade will, of course, be determined by thelength of the face of the roll upon which the doctor blade is tooperate, which may be twelve feet or more.

It may be appreciated that when doctor blades this long are urged intocontact with the roll at its ends it is extremely difficult, if notimpossible, to establish uniform pressure between the doctor blade andthe roll along the length of the doctor blade. There will be deflectionof the doctor blade along its length, the maximum deflection being inthe center of the roll which is the maximum distance from the forceproducing means which urge the doctor blade into contact with the roll.As will hereinafter be discussed, this deflection is somewhat analogousto the deflection of a beam between two points of support. Suchdeflection results in uneven pressure between the doctor blade and theroll along the length of the doctor blade and in turn causes heavyloading of the doctor blade against the rolls at the ends thereof andlight loading of the doctor blade toward the center thereof away fromthe ends of the doctor blade.

The ultimate result of such uneven pressure distribution along thelength of the doctor blade is severe wear on the end portions of theroll face with respect to the more central portion thereof. This isprobably one of the most prevalent reasons for periodically regrindingand recontouring rolls in paper mills.

In view of the foregoing problems experienced with presently knowncalender roll-doctor blade arrangements, the present invention isintended to provide a doctor blade structure through which asubstantially constant pressure between the doctor blade and the rollmay be obtained and maintained along the length of the doctor blade.

Accordingly, an object of this invention is to provide a new andimproved doctor blade.

Another object of this invention is to provide a new and improved doctorblade structure which will not create undesired wear in concentratedareas of the roll upon which it operates.

Another object of this invention is to provide a new and improved doctorblade assembly including means for maintaining the unit pressure of thedoctor blade on the roll upon which it operates substantially constantalong the length of the doctor blade.

3,327,341 Patented June 27, 1987 A further object of this invention isto provide a doctor blade assembly having a new and improved means forregulating the pressure between the doctor blade and the roll upon whichit operates.

Briefly stated, the invention in one form thereof comprises a hollowsleeve-like member upon which the doctor blade is mounted. The doctorblade mounting member is supported concentrically about and on a rigidshaft Which is rotatable to bring the doctor blade into contact with theroll upon which it operates. Fluid pressure operated means are providedbetween the doctor blade mounting member and the shaft to controllablydeflect the doctor blade mounting member along the length thereof andcompensate for deflection of the doctor blade and thereby maintainsubstantially constant the unit pressure of the doctor blade against theroll along the length of the doctor blade.

The features of the invention which are believed to be novel are setforth with particularity and definitely claimed in the concludingportion of this specification. The invention, however, both as to itsorganization and operation, together with further objects and advantagesthereof, may best be appreciated by reference to the following detaileddescription taken in conjunction with the drawings in which:

FIG. 1 is a front elevation of a calender including a doctor bladeassembly embodying the invention;

FIG. 2 is a sectional view seen in the plane of line 22 of FIG. 1

FIG. 3 is a sectional view seen in the plane of line 3-3 of FIG. 1;

FIG. 4 is a sectional view seen in the plane of line 4-4 of FIG. 3;

FIG. 5 is a view of a doctor blade seen in the plane of line 55 of FIG.3.

FIG. 6 is a sectional view seen along the plane of line 66 of FIG. 3with deflection imparted to the doctor blade support; and

FIG. 7 is a schematic diagram of a representative hydraulic circuitwhich may be utilized in the practice of the invention.

A calender utilizing adoctor blade assembly embodynecks or journals arerotatably supported in roll journal supports 12 and 13 carried on aframe illustrated as having leg portions 14. In a calendering operationroll 10 cooperates with other rolls thereabove exemplified by roll 15.It will be understood, of course, that a doctor blade is usuallyassociated with each rollof a calender. Carried on legs 14 or madeintegral therewith are doctor blade assembly supports 16. Each ofsupports 16 carries a guide member 17 thereon having a guide way 18therein. Slidably mounted on member 17 in guide ways 18 are bearingmounts 19. Bearing mounts 19 are adjustably positionable in guide ways18 by means of a locating bolt 20 as more clearly shown in FIG. 2. Bymeans of the guide member 17 and locating bolts 21) the doctor bladeassembly may be positioned a predetermined distance from the axis ofroll 10.

A doctor blade 22 is mounted in a holder 23 which in turn is mounted ona doctor blade carrier 24. Carrier 24 is mounted on a hollow shell-likedoctor blade support member 25 by means of a plurality of gussets orribs 26. Doctor blade support member 25 is mounted on and coaxiallyspaced about a shaft 27. Shaft 27 at each end thereof has securedthereto end caps 28 which receive therein bearing blocks 29 which reston a bearing 30 affixed to shaft 27. Shaft 27 at the ends thereof alsocarries thereon bearings 31 received in bearing mounts 19. Pinned toshaft 27 at either end thereof is the collar 32 of a lever =1! 33arranged to be actuated by the shaft or piston rod 34 of afluid-operated cylinder 35 which is carried on a bracket 36 extendingfrom each of supports 16. Levers 33 provide a means for cylinders 35 torotate shaft 27 and the doctor blade assembly thereon into engagementwith roll face 11, as indicated by the arc 37, FIG. 3. Mounted on shaft27 and secured thereto as by welding are striplike members 38 and 39which extend the length of shaft 27 between bearings 29. In theillustrated embodiment of the invention, the strip-like members 38 and39 are disposed substantially 180 degrees apart and define a planesubstantially parallel to the plane of the surface of doctor bladecarrier 24.

By virtue of the mounting of member 25 on shaft 27 through bearings 29,member 25 is normally rotatable on shaft 27. However, such rotation inone direction is prevented through the provision of torque transmittinglugs 40 which engage and butt against member 39 as most clearly shown inFIGS. 3 and 4. Lugs 40 are carried by member 25, for example, as bymeans of a headed bolt 41 threadably received into each lug.

The function of the torque transmitting lugs is to make the member 25follow the motion of the shaft when cylinders 35 are operated to urgethe doctor blade into engagement with the roll. It will be noted that asshaft 27 turns in the direction of the arrow A, FIG. 3, member 39 willact upon lugs 40 and produce equal and simultaneous rotation of member25. The lugs 40 are disposed at either end of member 25, although othersmay be spaced therebetween.

Member 25, shaft 27, and members 38 and 39 define a longitudinallyextending cavity. This cavity receives therein an expansible bladder 43.A fluid passage 44 is defined in member 25 and has a nipple 45 insertedtherein which provides communication to the interior of bladder 43. Inoperation, the cylinders 35 are actuated and the piston rods 34 thereofact on levers 33 connected to shaft 27 to rotate shaft 27 in thedirection of arrow A. As shaft 27 rotates member 39 thereon engages thelugs 40 and rotates member 25 together with doctor blade structurethereon and doctor blade 22 comes into engagement with face 11 of roll10. At this time, due to the long length of the doctor blade it willdeflect somewhat as exemplified in FIG. and the pressure between theedge of the doctor blade and the roll face will not be uniform along thelength of the doctor blade. In FIG. 5, the amount of deflection isexaggerated for purposes of illustration. This may be readilyappreciated by noting that the doctor blade is moved into contact withthe roll face by the exertion of equal forces which are essentially atthe ends thereof, the forces being exerted by the cylinders 35 andassociated mechanism. In FIG. 5 the forces exerted on the ends of thedoctor blade by the cylinders 35 are denoted by the arrows B and C. ItWill, of course, be understood that in the described structure theforces B and C reside without the ends of the doctor blade. However, forpurposes of discussion they may be considered to be located at the endsof the doctor blade. This deflection of the doctor blades results inuneven pressure along the length thereof and the roll will experiencegreater wear at the ends thereof.

To overcome this unequal distribution of pressure, bladder 43 isexpanded under fluid pressure and reacts against shaft 27 and members 38and 39 to deflect member 25, as shown in FIG. 6, in a directionsubstantially perpendicular to members 38 and 39 which is also generallyperpendicular to the plane of doctor blade support member 24. Thedeflection of member 25 is exaggerated for purposes of illustration.This deflection of member 25 due to the expansion of bladder 43, resultsin deflection of member 24 carried on member 25 and doctor blade 22carried thereon. This resultant deflection of doctor blade 22 is due tothe unit pressure exerted on the interior of member 25 by the pressurewithin bladder 43. It will be noted that the member 25 is supported atits ends on shaft 27 through bearing block 29 and bearing 30 andtherefore the deflection at the ends Will be zero, increasing to amaximum at the center. The resultant deflection of member 25 is that ofa beam uniformly loaded between two points of support. As member 25 isdeflected as shown in FIG. 6, the ribs 26 thereon move therewith andproduce deflection or bending of doctor blade carrier 24 along itslength. The maximum bending of carrier 24 occurs at its mid-point andthe curve thereof will follow the curve of carrier 24, FIG. 6. Thisdeflection or bending of carrier 24 and doctor blade 22 is in adirection opposite to the deflection of the doctor blade produced by theloading of the ends thereof by vectors B and C, FIG. 5 which representthe forces exerted on member 25 through shaft 27 by the cylinders 35.

The total force exerted by the fluid pressure on shaft 27 and member 25is selected to be approximately the same in magnitude as the total forceacting between the doctor blade and the roll produced by cylinders 35.Therefore, the pressure per unit length between the doctor blade and theroll along the length of the doctor blade is more likely to be constantand resultant bending of the doctor blade support tends to be prevented.It will, of course, be appreciated that slightly higher or lower fluidpressure in bladder 43 could be used as a secondary function in theevent that the calender operator might intentionally desire slightlyhigher contact pressure of the blade in the center of the roll or at theends of the roll under certain operating conditions.

A suitable means for applying fluid pressure to both the cylinders andbladder 43 is schematically illustrated in FIG. 7. This comprises a sump51, a pump 52, a pressure regulating valve 53, a two-position four-wayvalve 54, and a pressure changing cylinder 55. In operation the pump 52draws the fluid from sump 51 and applies it to a pressure regulatingvalve which determines the pressure at which the fluid will be appliedthe remainder of the system. The fluid is then applied to two-positionfourway valve 54 and hence to a coupling 56, and from coupling 56 tocylinders 35. When fluid is applied to cylinders 35 from coupling 56 thepiston shafts 34 are extended to move the doctor structure into contactwith the roll. At the same time the fluid under pressure is ap pliedfrom coupling 56 to pressure changing cylinder 55 to change the pressureapplied to the bladder in a predetermined ratio. The pressure applied tothe cylinders and bladder is determined by the setting ofpressure-regulating valve 53. When the pressure in the cylinders andbladder is to be reduced a new setting is made on pressureregulatingvalve 53, the two-position four-way valve 54 is shifted to its secondposition and operation reverse to that described takes place, in awell-known manner.

The structure of the pressure chamber and doctor blade support meansdisclosed herein is a preferred embodiment of the invention. Otherstructures including or defining a pressure chamber for deflecting orbending the doctor blade carrier which do not depart from the spirit andscope of the invention may occur to those skilled in the art.Accordingly, it is intended in the appended claims to cover allembodiments of the invention as well as modifications to the dis-closedembodiment of the invention which do not depart from the spirit andscope of the invention.

What is claimed is:

1. In a calender having a calender roll, a frame, means rotatablysupporting said calender roll on said frame and a doctor blade adaptedto contact the roll along the face thereof; a hollow tubular supportmember for said doctor blade extending along the length of the roll,means including a force reacting means defining an elongated pressurechamber within said member, and means for introducing fluid underpressure into said chamber to defleet said member and the doctor bladecarried thereon along their length, said chamber being so positionedwithin said hollow support member that the pressure in said,

chamber deflects said support member in a direction which urges thedoctor blade into contact with the roll along the length thereof.

2. In a calender having a calender roll, a frame, means rotatablysupporting said calender roll on said frame and a doctor blade adaptedto contact the roll along the face thereof; a hollow tubular supportmember for said doctor blade extending along the length of the roll,means at the ends of said support member for moving the support memberso that the doctor blade thereon contacts the roll, means including aforce reacting means defining an elongated chamber within said member,and means for introducing fluid under pressure into said chamber todeflect said member and the doctor blade carried thereon along theirlength, said chamber being so positioned within said hollow supportmember that the pressure in said chamber deflects said support member ina direction to urge the doctor blade into contact with the roll alongthe length thereof.

3. In a calender having a calender roll, a frame, means rotatablysupporting said calender roll on said frame and a doctor blade adaptedto contact the roll along the face thereof; a hollow tubular supportmember for said doctor blade extending along the length of the roll,means including a force reacting means defining an elongated pressurechamber within said member, and means for introducing fluid underpressure into said chamber to deflect said member and the doctor bladecarried thereon along their length, said chamber being so defined withinsaid hollow support member that the pressure in said chamber deflectssaid support member in a direction substantially perpendicular to theplane of the doctor blade.

4. In a calender having a calender roll, a frame, means rotatablysupporting said calender roll on said frame and a doctor blade adaptedto contact the roll along the face thereof; a shaft, means supportingsaid shaft on said frame, a hollow support member for said doctor bladeextending along the length of the roll and coaxially mounted on saidshaft, means at the ends of said shaft for rotating said shaft to movethe doctor blade on said support member into engagement with the roll,means carried by said shaft and cooperating with said support memberdefining an elongated chamber, and means for introducing fluid underpressure into said chamber to deflect said member and the doctor bladecarried thereon along their length, said chamber being so positionedwithin said hollow support member that the pressure in said chamberdeflects said support member in a direction to urge the doctor bladeinto contact with the roll along the length thereof.

5. The apparatus of claim 4 further including an expansible bladder insaid chamber to confine the fluid introduced therein.

6. 111 a calender having a calender roll, a frame, means rotatablysupporting said calender roll on said frame and a doctor blade adaptedto contact the roll along the face thereof; a support for the doctorblade comprising, a shaft, means rotatably supporting said shaft on saidframe, means acting at the ends of said shaft for rotating said shaft, asleeve-like member disposed about said shaft, and spaced therefrom todefine a cavity therebetween, said member carrying said doctor bladethereon, an elongated expansible bladder in said cavity adapted toconfine fluid under pressure, and means for introducing fluid underpressure into said bladder to expand said bladder so that saidsleeve-like member is displaced from its normal position with respect tosaid shaft, and said doctor blade on said member is urged toward thecalender roll to tend to substantially equalize the pressure between theblade and the roll along the length of the blade.

7. In a calender having a calender roll, a frame, means rotatablysupporting said calender roll on said frame and a doctor blade adaptedto contact the roll along the face thereof; a support for the doctorblade comprising, a shaft, means rotatably supporting said shaft on saidframe, means acting at the ends of said shaft for rotating said shaft, asleeve-like member normally coaxially disposed about said shaft andsupported thereon at its ends, said member carrying the doctor bladethereon, means carried on said shaft defining with said shaft and saidmember an elongated cavity, means for introducing fluid under pressureinto said cavity to deflect said member from its normal position withrespect to said shaft so that a doctor blade on said member is urgedtoward the calender roll to tend to substantially equalize the pressurebetween the blade and the roll along the length of the blade.

8. The arrangement of claim 7 further including an expansible bladder insaid cavity adapted to confine fluid under pressure.

9. The arrangement of claim 8 wherein said means carried on said shaftcomprise strips of material substantiaily extending along the length ofsaid shaft, said strips defining said cavity in such position relativeto the position of the doctor blade on said member that upon applicationof fluid pressure to said bladder said member is deflected in adirection substantially perpendicular to the plane of the doctor blade.

10. In a calender having a calender roll, a frame, means rotatablysupporting said calender roll on said frame and a doctor blade adaptedto contact the roll along the face thereof; a support for the doctorblade comprising, a shaft, means rotatably supporting said shaft on saidframe, a sleeve-like member coaxially disposed about said shaft andsupported at its ends on said shaft, said member carrying the doctorblade thereon in a plane substantially tangential to said member, meanscarried on said shaft defining a cavity along the length of said memberon the side of said shaft opposite the plane of the doctor blade, anexpansible bladder in said cavity adapted to confine fluid underpressure, means for rotating said shaft to bring the doctor blade intocontact with the roll, means for introducing fluid under pressure intosaid bladder to expand said bladder so that said member is displacedfrom its normal position with respect to said shaft and said doctorblade on said member is urged toward the calender roll to tend tosubstantially equalize the pressure between the blade and the roll alongthe length of the blade.

References Cited UNITED STATES PATENTS 2,330,889 10/1943 Holcomb15256.51 3,087,185 4/1963 Washburn 15256.51 3,131,092 4/1964 Coghill118-413 3,163,878 1/1965 Smith et a1. 15-25651 CHARLES A. WILLMUTH,Primary Examiner.

L. G. MACHLIN, Examiner.

1. IN A CALENDER HAVING A CALENDER ROLL, A FRAME, MEANS ROTATABLYSUPPORTING SAID CALENDER ROLL ON SAID FRAME AND A DOCTOR BLADE ADAPTEDTO CONTACT THE ROLL ALONG THE FACE THEREOF; A HOLLOW TUBULAR SUPPORTMEMBER FOR SAID DOCTOR BLADE EXTENDING ALONG THE LENGTH OF THE ROLL,MEANS INCLUDING A FORCE REACTING MEANS DEFINING AN ELONGATED PRESSURECHAMBER WITHIN SAID MEMBER, AND MEANS FOR INTRODUCING FLUID UNDERPRESSURE INTO SAID CHAMBER TO DEFLECT SAID MEMBER AND THE DOCTOR BLADECARRIED THEREON ALONG THEIR LENGTH, SAID CHAMBER BEING SO POSITIONEDWITHIN SAID HOLLOW SUPPORT MEMBER THAT THE PRESSURE IN SAID CHAMBERDEFLECTS SAID SUPPORT MEMBER IN A DIRECTION WHICH URGES THE DOCTOR BLADEINTO CONTACT WITH THE ROLL ALONG THE LENGTH THEREOF.